n = int(input())
c = list(input())
r = c.count('R')
w = c.count('W')
ans = 0

for i in range(r):
    if c[i] == 'R':
        pass
    elif c[i] == 'W':
        ans += 1
print(ans) n = int(input()) n int(input()) int input() input c = list(input()) c list(input()) list input() input r = c.count('R') r c.count('R') c.count c count 'R' w = c.count('W') w c.count('W') c.count c count 'W' ans = 0 ans 0 for i in range(r):
    if c[i] == 'R':
        pass
    elif c[i] == 'W':
        ans += 1 i range(r) range r if c[i] == 'R':
        pass
    elif c[i] == 'W':
        ans += 1 c[i] == 'R' c[i] c i 'R' elif c[i] == 'W':
        ans += 1 c[i] == 'W' c[i] c i 'W' ans += 1 ans 1 print(ans) print ans r = c.count('R') c.count('R') r ans = 0 0 ans c = list(input()) list(input()) c w = c.count('W') c.count('W') w ans += 1 1 ans n = int(input()) int(input()) n
n = int(input())
c = list(input())
r = c.count('R')
w = c.count('W')
ans = 0

for i in range(r):
    if c[i] == 'R':
        pass
    elif c[i] == 'W':
        ans += 1
print(ans)